Photoelectrochemical aptasensing of thrombin based on multilayered gold nanoparticle/graphene-TiO 2 and enzyme functionalized graphene oxide nanocomposites

Sandwich photoelectrochemical biosensing of concanavalin A based on CdS/AuNPs/NiO Z-scheme heterojunction and lectin-sugar binding

A CdS/AuNPs/NiO Z-scheme heterojunction was prepared on a fluorine-doped tin oxide (FTO) electrode by hydrothermal synthesis of NiO on FTO, electrodeposition of AuNPs on NiO/FTO electrode and then cast-coating of CdS quantum dots. The CdS/AuNPs/NiO/FTO electrode gave a notably increased photocurrent versus NiO/FTO, CdS/FTO, AuNPs/NiO/FTO, CdS/AuNPs/FTO and CdS/NiO/FTO electrodes. The CdS/AuNPs/NiO/FTO electrode was further cast-coated with chitosan to immobilize d-mannose by Schiff base reaction, and concanavalin A (ConA) and then horseradish peroxidase (HRP) were captured on the electrode surface by lectin-sugar binding. 4-Chloro-1-naphthol (4-CN) was oxidized to form an insoluble precipitate catalyzed by HRP in the presence of H₂O₂, and the presence of precipitate on the photoelectrode inhibited the photocurrent in the presence of holes scavenger ascorbic acid. The relevant electrodes were characterized by electrochemistry, quartz crystal microbalance (QCM), UV-vis spectrophotometry, scanning electron microscopy/energy dispersive spectroscopy, and transmission electron microscopy. The QCM revealed that the collection efficiency (η) of the 4-CN-electrooxidation precipitate on the electrode can be as high as 91.8%. Under the optimal conditions, the decline of photocurrent responded linearly to the common logarithm of ConA concentration from 50 pM to 500 nM, with a limit of detection of 17 pM (S/N = 3). Satisfactory results were obtained in the detection of real soybean samples.

Simple and sensitive nitric oxide biosensor based on the electrocatalysis of horseradish peroxidase on AuNPs@metal-organic framework composite-modified electrode

Fe-based metal–organic framework (MIL-101(Fe)) was synthesized through a simple solvothermal synthesis and then used to prepare the AuNPs-decorated MIL-101(Fe) nanocomposite (APPPM(Fe)) by a multi-step layer-by-layer assembly process. Benefited from the porous structure of MIL-101(Fe) and the multilayer assemble process, the loading amount of AuNPs on APPPM(Fe) was enhanced and exhibited a fine biocompatible interface and high conductivity. Through the intense Au–S bond, high loading amount of horseradish peroxidase was immobilized on APPPM(Fe) and the native bioactivity of HRP was kept to realize its direct electrochemistry. From the electrochemical kinetics, the constructed biosensor displayed fast electron transfer and good electrocatalysis activity for the detection of nitric oxide (NO) with wide linear range from 0.033 to 5370 μM and a low detection limit of 0.01 μM (3 σ) as well as fine stability, reproducibility and specificity. According to results of real sample analysis, the proposed electrochemical biosensor offers fast and simple detection of NO in real serum. Therefore, the present strategy definitely provided a potential application prospect in NO clinic detection and disease therapy.

Voltammetric kanamycin aptasensor based on the use of thionine incorporated into Au@Pt core-shell nanoparticles

A signal-on aptasensor is described for the voltammetric determination of kanamycin (KANA). Au@Pt core-shell nanoparticles with large surface and good electrical conductivity were synthetized and act as both a conductive material and as the carrier for complementary strands (CS2) and thionine (TH). In the presence of KANA, the electrochemical response of TH changes due to hybridization between CS1 immobilized on the electrode and the Au@Pt-CS2/TH system. The peak current increases linearly with the logarithm of the KANA concentration in the range from 1 pM to 1 μM, and the limit of detection is 0.16 pM. The sensor was characterized in terms of selectivity, reproducibility and stability, and satisfactory results were obtained. It was also utilized for the determination of KANA in (spiked) chicken samples. The recoveries (95.8-103.2%) demonstrate the potential of the method for KANA detection in real samples. Graphical abstract A signal-on aptasensor for kanamycin (KANA) was developed by using Au@Pt core-shell nanoparticles as nanocarrier for probe aptamer and as a sensing probe.

Synthesis of a novel graphene-based gold nanocomposite using PVEIM-b-PNIPAM as a stabilizer and its thermosensitivity for the catalytic reduction of 4-nitrophenol

Fabrication of a graphene-based gold nanocomposite using PVEIM-b-PNIPAM as a stabilizer and its thermosensitivity for the reduction of 4-nitrophenol.

A ratiometric photoelectrochemical immunosensor based on g-C3N4@TiO2 NTs amplified by signal antibodies–Co3O4 nanoparticle conjugates

Herein, we report a ratiometric photoelectrochemical (PEC) immunosensor coupled with secondary antibodies–Co₃O₄ nanoparticle conjugates (Ab₂–Co₃O₄ NPs) for signal amplification.